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  • H10K85/322—Metal complexes comprising a group IIIA element, e.g. Tris (8-hydroxyquinoline) gallium [Gaq3] comprising boron
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  • H10K85/342—Transition metal complexes, e.g. Ru(II)polypyridine complexes comprising iridium
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  • H10K2101/00—Properties of the organic materials covered by group H10K85/00
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  • H10K50/11—OLEDs or polymer light-emitting diodes [PLED] characterised by the electroluminescent [EL] layers
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  • H10K85/211—Fullerenes, e.g. C60
  • H10K85/215—Fullerenes, e.g. C60 comprising substituents, e.g. PCBM
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  • Y02E10/00—Energy generation through renewable energy sources
  • Y02E10/50—Photovoltaic [PV] energy
  • Y02E10/549—Organic PV cells

Definitions

• the present disclosure generally relates to electrically active, optically active, solar, and semiconductor devices and, in particular, to organic photosensitive optoelectronic devices comprising at least one acceptor and/or donor energy sensitizer. Also disclosed herein are methods of preparing the same.
• Photosensitive optoelectronic devices rely on the optical and electronic properties of materials to either produce or detect electromagnetic radiation electronically or to generate electricity from ambient electromagnetic radiation.
• Photosensitive optoelectronic devices convert electromagnetic radiation into electricity.
• Solar cells also called photovoltaic (PV) devices, are a type of photosensitive optoelectronic device that is specifically used to generate electrical power.
• PV devices which may generate electrical energy from light sources other than sunlight, can be used to drive power consuming loads to provide, for example, lighting, heating, or to power electronic circuitry or devices such as calculators, radios, computers or remote monitoring or communications equipment.
• resistive load refers to any power consuming or storing circuit, device, equipment or system.
• Another type of photosensitive optoelectronic device is a
• signal detection circuitry monitors the resistance of the device to detect changes due to the absorption of light.
• Another type of photosensitive optoelectronic device is a
• a photodetector In operation, a photodetector is used in conjunction with a current detecting circuit which measures the current generated when the photodetector is exposed to electromagnetic radiation and may have an applied bias voltage.
• a detecting circuit as described herein is capable of providing a bias voltage to a photodetector and measuring the electronic response of the photodetector to electromagnetic radiation.
• These three classes of photosensitive optoelectronic devices may be characterized according to whether a rectifying junction as defined below is present and also according to whether the device is operated with an external applied voltage, also known as a bias or bias voltage.
• a photoconductor cell does not have a rectifying junction and is normally operated with a bias.
• a PV device has at least one rectifying junction and is operated with no bias.
• a photodetector has at least one rectifying junction and is usually but not always operated with a bias.
• a photovoltaic cell provides power to a circuit, device or equipment, but does not provide a signal or current to control detection circuitry, or the output of information from the detection circuitry.
• photoconductor provides a signal or current to control detection circuitry, or the output of information from the detection circuitry but does not provide power to the circuitry, device or equipment.
• photosensitive optoelectronic devices have been constructed of a number of inorganic semiconductors, e.g., crystalline, polycrystalline and amorphous silicon, gallium arsenide, cadmium telluride and others.
• semiconductor denotes materials which can conduct electricity when charge carriers are induced by thermal or electromagnetic excitation.
• photoconductive generally relates to the process in which electromagnetic radiant energy is absorbed and thereby converted to excitation energy of electric charge carriers so that the carriers can conduct, i.e., transport, electric charge in a material.
• photoconductor and “photoconductive material” are used herein to refer to semiconductor materials which are chosen for their property of absorbing electromagnetic radiation to generate electric charge carriers.
• PV devices may be characterized by the efficiency with which they can convert incident solar power to useful electric power.
• Devices utilizing crystalline or amorphous silicon dominate commercial applications, and some have achieved efficiencies of 23% or greater.
• efficient crystalline-based devices, especially of large surface area are difficult and expensive to produce due to the problems inherent in producing large crystals without significant efficiency-degrading defects.
• high efficiency amorphous silicon devices still suffer from problems with stability.
• Present commercially available amorphous silicon cells have stabilized efficiencies between 4 and 8%. More recent efforts have focused on the use of organic photovoltaic cells to achieve acceptable photovoltaic conversion efficiencies with economical production costs.
• PV devices may be optimized for maximum electrical power generation under standard illumination conditions (i.e., Standard Test Conditions which are 1000 W/m 2 , AM1 .5 spectral illumination), for the maximum product of photocurrent times photovoltage.
• standard illumination conditions i.e., Standard Test Conditions which are 1000 W/m 2 , AM1 .5 spectral illumination
• the power conversion efficiency of such a cell under standard illumination conditions depends on the following three parameters: (1 ) the current under zero bias, i.e., the short-circuit current Isc, in Amperes (2) the photovoltage under open circuit conditions, i.e., the open circuit voltage Voc, in Volts and (3) the fill factor, FF.
• PV devices produce a photo-generated current when they are connected across a load and are irradiated by light.
• a PV device When irradiated under infinite load, a PV device generates its maximum possible voltage, V open-circuit, or Voc- When irradiated with its electrical contacts shorted, a PV device generates its maximum possible current, I short-circuit, or Isc- When actually used to generate power, a PV device is connected to a finite resistive load and the power output is given by the product of the current and voltage, I * V.
• the maximum total power generated by a PV device is inherently incapable of exceeding the product, Isc x Voc- When the load value is optimized for maximum power extraction, the current and voltage have the values, Lax and V max , respectively.
• a figure of merit for PV devices is the fill factor, FF, defined as:
• FF ⁇ l max V max ⁇ / ⁇ Isc Voc ⁇ (1 )
• FF is always less than 1 , as Isc and Voc are never obtained simultaneously in actual use. Nonetheless, as FF approaches 1 , the device has less series or internal resistance and thus delivers a greater percentage of the product of Isc and V 0 c to the load under optimal conditions.
• Pi nc is the power incident on a device
• the power efficiency of the device, ⁇ ⁇ may be calculated by:
• n-type denotes that the majority carrier type is the electron. This could be viewed as the material having many electrons in relatively free energy states.
• p-type denotes that the majority carrier type is the hole. Such material has many holes in relatively free energy states.
• the type of the background, i.e., not photo-generated, majority carrier concentration depends primarily on unintentional doping by defects or impurities. The type and
• concentration of impurities determine the value of the Fermi energy, or level, within the gap between the conduction band minimum and valance band maximum energies, also known as the HOMO-LUMO gap.
• the Fermi energy characterizes the statistical occupation of molecular quantum energy states denoted by the value of energy for which the probability of occupation is equal to 1 ⁇ 2.
• a Fermi energy near the conduction band minimum (LUMO) energy indicates that electrons are the predominant carrier.
• a Fermi energy near the valence band maximum (HOMO) energy indicates that holes are the predominant carrier. Accordingly, the Fermi energy is a primary characterizing property of traditional semiconductors and the prototypical PV junction has traditionally been the p-n interface.
• rectifying denotes, inter alia, that an interface has an asymmetric conduction characteristic, i.e., the interface supports electronic charge transport preferably in one direction. Rectification is associated normally with a built- in electric field which occurs at the junction between appropriately selected materials.
• the terms “donor” and “acceptor” refer to the relative positions of the HOMO and LUMO energy levels of two contacting but different organic materials. This is in contrast to the use of these terms in the inorganic context, where “donor” and “acceptor” may refer to types of dopants that may be used to create inorganic n- and p- types layers, respectively.
• donor and “acceptor” may refer to types of dopants that may be used to create inorganic n- and p- types layers, respectively.
• the LUMO energy level of one material in contact with another is lower, then that material is an acceptor. Otherwise it is a donor. It is energetically favorable, in the absence of an external bias, for electrons at a donor-acceptor junction to move into the acceptor material, and for holes to move into the donor material.
• a significant property in organic semiconductors is carrier mobility. Mobility measures the ease with which a charge carrier can move through a conducting material in response to an electric field.
• a layer including a material that conducts preferentially by electrons due to a high electron mobility may be referred to as an electron transport layer, or ETL.
• a layer including a material that conducts preferentially by holes due to a high hole mobility may be referred to as a hole transport layer, or HTL.
• an acceptor material may be an ETL and a donor material may be an HTL.
• heterojunction may also play an important role.
• the energy level offset at an organic donor-acceptor (D-A) heterojunction is believed to be important to the operation of organic PV devices due to the fundamental nature of the photogeneration process in organic materials.
• D-A organic donor-acceptor
• Upon optical excitation of an organic material localized Frenkel or charge-transfer excitons are generated.
• the bound excitons must be dissociated into their constituent electrons and holes.
• Such a process can be induced by the built-in electric field, but the efficiency at the electric fields typically found in organic devices (F ⁇ 10 6 V/cm) is low.
• the most efficient exciton dissociation in organic materials occurs at a D-A interface.
• the donor material with a low ionization potential forms a heterojunction with an acceptor material with a high electron affinity.
• the dissociation of the exciton can become energetically favorable at such an interface, leading to a free electron polaron in the acceptor material and a free hole polaron in the donor material.
• the diffusion length (L D ) of an exciton is typically much less (L D ⁇ 50 A) than the optical absorption length (-500 A), requiring a tradeoff between using a thick, and therefore resistive, cell with multiple or highly folded interfaces, or a thin cell with a low optical absorption efficiency.
• Organic PV cells have many potential advantages when compared to traditional silicon-based devices.
• Organic PV cells are light weight, economical in materials use, and can be deposited on low cost substrates, such as flexible plastic foils.
• the reported efficiencies of some of the best organic PVs are approaching 9%.
• device efficiencies must further improve via new material and device design approaches.
• organic photosensitive optoelectronic devices comprising acceptor and/or donor sensitizers to increase absorption and photoresponse of acceptor and/or donor layers, respectively.
• an organic photosensitive optoelectronic device comprises two electrodes in superposed relation; a mixed organic acceptor layer and an organic donor layer located between the two electrodes, wherein the mixed organic acceptor layer comprises a mixture of an acceptor material and at least one acceptor sensitizer, wherein the acceptor material and the at least one acceptor sensitizer are chosen to satisfy the following conditions:
• the at least one acceptor sensitizer has a lowest triplet excited state (E T - ASens) greater than or equal to a lowest triplet excited state energy (E T- A) of the acceptor material;
• the at least one acceptor sensitizer has a reduction potential lower than or equal to a reduction potential of the acceptor material
• the at least one acceptor sensitizer and the acceptor material form a charge transfer (CT) state having a CT state energy
• the CT state energy is greater than or equal to the lowest triplet excited state energy (ET-A) of the acceptor material.
• the acceptor material and the at least one acceptor sensitizer are chosen such that the at least one acceptor sensitizer has a lowest singlet excited state energy (E S -ASens) greater than or equal to a lowest singlet excited state energy (ES-A) of the acceptor material.
• E S -ASens lowest singlet excited state energy
• ES-A lowest singlet excited state energy
• the acceptor material and the at least one acceptor sensitizer are chosen such that the CT state energy is greater than or equal to a lowest singlet excited state energy (ES-A) of the acceptor material.
• ES-A lowest singlet excited state energy
• the mixture of the acceptor material and the at least one acceptor sensitizer form a solid solution.
• the at least one acceptor sensitizer has an absorptivity of at least 10 3 cm "1 at one or more wavelengths ranging from 350 to 950 nm.
• the at least one acceptor sensitizer has a maximum absorptivity at one or more wavelengths, the maximum absorptivity being at least twice as large as an absorptivity of the acceptor material at the one or more wavelengths.
• the acceptor material is chosen from fullerenes and fullerene derivatives.
• the at least one acceptor sensitizer is chosen from phthalocyanines, subphthalocyanines, dipyrrins and metal complexes thereof, porphyrins, azadipyrrins and metal complexes thereof, boron dipyrromethene (BODIPY) dyes, and derivatives thereof.
• the acceptor material is chosen from fullerenes and fullerene derivatives
• the at least one acceptor sensitizer is chosen from phthalocyanines, subphthalocyanines, dipyrrins and metal complexes thereof, porphyrins, azadipyrrins and metal complexes thereof, boron dipyrromethene (BODIPY) dyes, and derivatives thereof.
• the organic photosensitive optoelectronic device further comprises an intermediate acceptor layer located between the mixed acceptor layer and the donor layer, wherein the intermediate acceptor layer consists of the acceptor material and forms a donor-acceptor heterojunction with the donor layer.
• the at least one acceptor sensitizer comprises two or more sensitizers.
• the organic donor layer is a mixed organic donor layer comprising a mixture of a donor material and at least one donor sensitizer, wherein the donor material and the at least one donor sensitizer are chosen to satisfy the following conditions: the at least one donor sensitizer has a lowest triplet excited state energy ( ⁇ -DSens) greater than or equal to a lowest triplet excited state energy (E T- D) of the donor material;
• the at least one donor sensitizer has an oxidation potential higher than or equal to an oxidation potential of the donor material
• the at least one donor sensitizer and the donor material form a charge transfer (CT) state having a CT state energy
• CT state energy is greater than or equal to the lowest triplet excited state energy (E T- D) of the donor material.
• the donor material and the at least one donor sensitizer are chosen such that the at least one donor sensitizer has a lowest singlet excited state energy (E S -DSens) greater than or equal to a lowest singlet excited state energy (E S- D) of the donor material.
• E S -DSens lowest singlet excited state energy
• E S- D lowest singlet excited state energy
• the donor material and the at least one donor sensitizer are chosen such that the CT state energy is greater than or equal to a lowest singlet excited state energy (ES-D) of the donor material.
• E-D lowest singlet excited state energy
• the organic photosensitive optoelectronic device comprises an intermediate donor layer located between the mixed organic donor layer and the mixed organic acceptor layer, wherein the intermediate donor layer consists of the donor material and forms a donor-acceptor heterojunction with the mixed organic acceptor layer.
• the organic photosensitive optoelectronic device comprises an intermediate acceptor layer and an intermediate donor layer, wherein the intermediate acceptor layer consists of the acceptor material and is adjacent to the mixed organic acceptor layer, and the intermediate donor layer consists of the donor material and is adjacent to the mixed organic donor layer, both intermediate layers being positioned between the mixed organic acceptor layer and the mixed organic donor layer.
• the intermediate acceptor layer and the intermediate donor layer form a donor-acceptor heterojunction.
• an organic photosensitive optoelectronic device comprises two electrodes in superposed relation; an organic acceptor layer and a mixed organic donor layer located between the two electrodes, wherein the mixed organic donor layer comprises a mixture of a donor material and at least one donor sensitizer, wherein the donor material and the at least one donor sensitizer are chosen to satisfy the following conditions:
• the at least one donor sensitizer has a lowest triplet excited state energy ( ⁇ -DSens) greater than or equal to a lowest triplet excited state energy (E T- D) of the donor material;
• the at least one donor sensitizer has an oxidation potential greater than or equal to an oxidation potential of the donor material
• the at least one donor sensitizer and the donor material form a charge transfer (CT) state having a CT state energy
• CT state energy is greater than or equal to the lowest triplet excited state energy (E T- D) of the donor material.
• the donor material and the at least one donor sensitizer are chosen such that the at least one donor sensitizer has a lowest singlet excited state energy (E S -DSens) greater than or equal to a lowest singlet excited state energy (ES-D) of the donor material.
• the donor material and the at least one donor sensitizer are chosen such that the CT state energy is greater than or equal to a lowest singlet excited state energy (E S-D ) of the donor material.
• the mixture of the donor material and the at least one donor sensitizer form a solid solution.
• the at least one donor sensitizer has an absorptivity of at least 10 3 cm "1 at one or more wavelengths ranging from 350 to 950 nm.
• the organic photosensitive optoelectronic device further comprises an intermediate donor layer located between the mixed donor layer and the acceptor layer, wherein the intermediate donor layer consists of the donor material and forms a donor-acceptor heterojunction with the acceptor layer.
• photosensitive optoelectronic device comprising depositing a photoactive region over a first electrode, and depositing a second electrode over the photoactive region, wherein the photoactive region comprises a mixed organic acceptor layer and an organic donor layer, wherein the mixed organic acceptor layer comprises a mixture of an acceptor material and at least one acceptor sensitizer, the acceptor material and the at least one acceptor sensitizer being chosen to satisfy the following conditions:
• the at least one acceptor sensitizer has a lowest triplet excited state
• E T -ASens energy greater than or equal to a lowest triplet excited state energy (E T -A) of the acceptor material
• E T -A lowest triplet excited state energy
• the at least one acceptor sensitizer and the acceptor material form a charge transfer (CT) state having a CT state energy
• the CT state energy is greater than or equal to the lowest triplet excited state energy (E T- A) of the acceptor material.
• the deposition of a photoactive region over a first electrode comprises depositing the organic donor layer over the first electrode; and co-depositing the acceptor material and the at least one acceptor sensitizer over the first electrode, wherein the co-deposition over the first electrode occurs before or after the deposition of the organic donor layer over the first electrode.
• the acceptor material and the at least one acceptor sensitizer are co-deposited at an acceptonsensitizer ratio in the range of 10:1 to 1 :2.
• the photoactive region further comprises an intermediate acceptor layer located between the mixed organic acceptor layer and the organic donor layer, wherein the intermediate acceptor layer consists of the acceptor material.
• the deposition of a photoactive region over a first electrode may comprise depositing the organic donor layer over the first electrode; depositing the intermediate acceptor layer over the first electrode; and co- depositing the acceptor material and the at least one acceptor sensitizer over the first electrode, wherein the co-deposition over the first electrode occurs before or after the deposition of the organic donor layer, and wherein the deposition of the intermediate acceptor layer results in the intermediate acceptor layer being positioned between the mixed organic acceptor layer and the organic donor layer.
• the organic donor layer is a mixed organic donor layer as described herein.
• the deposition of a photoactive region over a first electrode may comprise co-depositing the donor material and the at least one donor sensitizer over the first electrode, and co-depositing the acceptor material and the at least one acceptor sensitizer over the first electrode, wherein the co-deposition of the acceptor material and the at least one acceptor sensitizer occurs before or after the co-deposition of the donor material and the at least one donor sensitizer.
• the acceptor material and the at least one acceptor sensitizer are co-deposited at an acceptonsensitizer ratio in a range of 10:1 to 1 :2, and the donor material and the at least one donor sensitizer are co-deposited at a dononsensitizer ratio in a range of 10:1 to 1 :2.
• the photoactive region further comprises an intermediate acceptor layer and an intermediate donor layer, wherein the
• intermediate acceptor layer consists of the acceptor material and is adjacent to the mixed organic acceptor layer
• intermediate donor layer consists of the donor material and is adjacent to the mixed organic donor layer, both intermediate layers being positioned between the mixed organic donor layer and the mixed organic acceptor layer.
• the intermediate acceptor layer and the intermediate donor layer may form a donor-acceptor heterojunction.
• the deposition of a photoactive region over a first electrode may comprise co-depositing the donor material and the at least one donor sensitizer over the first electrode; depositing the intermediate donor material over the first electrode; depositing the intermediate acceptor material over the first electrode; and co-depositing the acceptor material and the at least one acceptor sensitizer over the first electrode, wherein the co-deposition of the acceptor material and the at least one acceptor sensitizer occurs before or after the co- deposition of the donor material and the at least one donor sensitizer, and wherein the deposition of the intermediate acceptor layer results in the intermediate acceptor layer being positioned adjacent the mixed organic acceptor layer, and the deposition of the intermediate donor layer results in the intermediate donor layer being positioned adjacent the mixed organic donor layer, both intermediate layers being positioned between the mixed organic donor layer and the mixed organic acceptor layer.
• Figure 1 shows a schematic of an organic photosensitive
• optoelectronic device comprising an organic mixed acceptor layer in accordance with the present disclosure.
• Figure 2 shows energy sensitization pathways following excitation of a sensitizer using Cm as an exemplary acceptor material, where 2A shows Forster (singlet-singlet) energy transfer; 2B shows Dexter (triplet-triplet) energy transfer; and 2C shows electron transfer via a charge transfer state.
• Energy transfer EnT
• intersystem crossing ISC
• EIT electron transfer
• CT charge transfer
• Figure 3 shows a schematic of an organic photosensitive
• optoelectronic device comprising an organic mixed acceptor layer and an organic mixed acceptor layer
• Figure 4 shows a schematic of an organic photosensitive
• optoelectronic device comprising an organic mixed donor layer in accordance with the present disclosure.
• Figure 5 shows a schematic of an organic photosensitive
• optoelectronic device comprising an organic mixed donor layer and an intermediate donor layer in accordance with the present disclosure.
• Figure 6 shows a schematic of an organic photosensitive
• optoelectronic device comprising an organic mixed acceptor layer and an organic mixed donor layer in accordance with the present disclosure.
• Figure 7 shows a schematic of an organic photosensitive
• optoelectronic device comprising an organic mixed acceptor layer, an organic mixed donor layer, an intermediate acceptor layer, and an intermediate donor layer in accordance with the present disclosure.
• Figure 8 shows a schematic of a photoactive region deposited over a first electrode and a second electrode deposited over the photoactive region.
• Figure 9 shows a synthesis and structure for a chlorinated zinc dipyrrin compound (ZCI).
• Figure 10 shows an Ortep diagram of ZCI and space filling models of Qso and ZCI in single crystals.
• Figure 11A shows absorption (solid square) and emission (open circle) spectra of ZCI in methyl cyclohexane at room temperature; 11 B shows an emission spectrum of ZCI in 2-methyl tetrahydrofuran at 77K (inset is emission from the triplet state of ZCI); 11 C shows absorption (solid symbols) and emission (open symbol) under excitation at 500 nm of C6o film (square) and ZCI film (triangle); and 11 D shows cyclic voltammetry (CV) and differential pulse voltammetry (DPV) diagrams of ZCI in dichloromethane (vs. Fc7Fc) (scan rate at 100 mV/s).
• CV cyclic voltammetry
• D differential pulse voltammetry
• Figure 12 shows a synthesis and structure of an iridium dipyrrin compound (IrDP).
• Figure 13A shows absorption (solid symbol) and emission (open symbol) of IrDP in dichloromethane solution under N2 at room temperature (square) and at 77K (circle); 13B shows a cyclic voltammetry diagram for IrDP (scan rate at 100 mV/s); and 13C shows absorption (solid symbols) of a C 6 o film (square) and an IrDP film (triangle) and emission (open symbol) of IrDP under excitation at 500 nm.
• Figure 14A shows absorption (solid symbols) and emission (open symbols) under laser excitation at 517 nm of 50 nm Ceo (circle), 50 nm of Ceo mixed with 9 nm of ZCI (15% v/v) (triangle) and 50 nm of C 60 mixed with 25 nm of ZCI (33% v/v) (square) and 14B depicts Forster energy transfer from ZCI to Ceo-
• Figure 15 shows a schematic of a reference device and a device using an acceptor sensitizer at varying amounts.
• Figure 16 shows performance characteristics of an organic PV device using ZCI as a sensitizer, where 16A shows current-voltage characteristics under 1 sun AM 1 .5G illumination and 16B shows external quantum efficiency (EQE) measurements of reference device D1 and the sensitized device (D2) (C6o:ZCI at 30 nm : 6 nm, 17% v/v).
• EQE external quantum efficiency
• Figure 17 shows performance characteristics of an organic PV device using IrDP as a sensitizer, where 17A shows current-voltage characteristics under 1 sun AM 1 .5G illumination and 17B shows external quantum efficiency (EQE) measurements of reference device D1 and the sensitized device (D2) (C6o:lrDP at 30 nm : 6 nm, 17% v/v).
• EQE external quantum efficiency
• Figure 18 shows performance characteristics of an organic PV device using F-
• EQE external quantum efficiency
• Figure 19 shows performance characteristics of an organic PV device using CleSubPc as a sensitizer, where 19A shows current-voltage characteristics under 1 sun AM 1 .5G illumination and 19B shows external quantum efficiency (EQE) measurements of reference device D1 and the sensitized device (D2) (Ceo- CleSubPc at 30 nm : 6 nm, 17% v/v).
• EQE external quantum efficiency
• Figure 20 summarizes the performance characteristics of the organic PV devices using different sensitizers: ITO/NPD (1 1 nm)/C 6 o (5 nm)/ S:C 6 o (t nm : 30 nm, x %, v/v)/C6o (5 nm)/BCP (10 nm)/AI, and the corresponding reference devices, ITO/NPD (1 1 nm)/C 6 o (40 nm)/BCP (10 nm)/AI under simulated 1 sun AM1 .5G illumination.
• Figure 21 A shows a schematic of a reference device and a schematic of a device with a mixed C6o:ZCI layer on top of a neat Cm layer, the layers having various thicknesses;
• 21 B shows current-voltage characteristics for the devices under 1 sun AM 1 .5G illumination;
• Figure 23A shows the structure of squaraine (SQ) used as a donor layer
• 23B shows a schematic of a reference device and a schematic of a device with a mixed C6o:ZCI layer and a squaraine (SQ) donor layer
• 23C shows current- voltage characteristics under 1 sun AM1 .5G illumination and EQE measurements
• 23D summarizes the performance characteristics of the devices.
• Figure 24A shows thin film extinction coefficients of Cm, ZCI, CleSubPc, C 6 o:ZCI:CI 6 SubPc, and DPSQ compared with the AM 1 .5G solar spectrum; and 24B show emission spectra of ZCI and CleSubPc compared with the absorption of Ceo-
• Figure 25 shows singlet and triplet energies of ZCI, CleSubPc, and Ceo with arrows indicating energy transfer pathways and reduction potentials (vs Fc/Fc + ) of Ceo, ZCI, and CleSubPc.
• Figure 26A shows a schematic of a reference device and a device utilizing multiple sensitizers
• 26B shows J-V curves of devices under one sun AM 1 .5G illumination and EQE measurements with absorption spectra of ZCI and CleSubPc added for reference
• 26C summarizes the performance characteristics of the devices.
• Figure 27A shows a schematic of a reference device and a device utilizing a donor sensitizer
• 27B shows J-V curves of devices under one sun AM 1 .5G illumination and EQE measurements
• 27C summarizes the
• organic includes polymeric materials as well as small molecule organic materials that may be used to fabricate organic photosensitive devices.
• Small molecule refers to any organic material that is not a polymer, and "small molecules” may actually be quite large. Small molecules may include repeat units in some circumstances. For example, using a long chain alkyl group as a substituent does not remove a molecule from the "small molecule” class. Small molecules may also be incorporated into polymers, for example as a pendent group on a polymer backbone or as a part of the backbone.
• lowest triplet excited state energy means the triplet excited state energy closest to the ground state energy.
• lowest singlet excited state energy means the singlet excited state energy closest to the ground state energy.
• co-depositing or “co-deposition” means a process of depositing materials to produce a solid solution. Materials may be “co- deposited” according to a variety of methods. “Co-depositing” or “co-deposition” may include, for example, simultaneously or sequentially depositing materials
• Electrode and “contact” are used herein to refer to a layer that provides a medium for delivering photo-generated current to an external circuit or providing a bias current or voltage to the device.
• an electrode, or contact provides the interface between the active regions of an organic photosensitive optoelectronic device and a wire, lead, trace or other means for transporting the charge carriers to or from the external circuit.
• Anodes and cathodes are examples.
• U.S. Patent No. 6,352,777, incorporated herein by reference for its disclosure of electrodes, provides examples of electrodes, or contacts, which may be used in a photosensitive optoelectronic device.
• At least one of the electrical contacts should be minimally absorbing and minimally reflecting of the incident electromagnetic radiation.
• a contact should be transparent or at least semi-transparent.
• An electrode is said to be “transparent” when it permits at least 50% of the ambient electromagnetic radiation in relevant wavelengths to be transmitted through it.
• An electrode is said to be “semi-transparent” when it permits some, but less that 50% transmission of ambient electromagnetic radiation in relevant wavelengths.
• the opposing electrode may be a reflective material so that light which has passed through the cell without being absorbed is reflected back through the cell.
• a "layer” refers to a member or component of a photosensitive device whose primary dimension is X-Y, i.e., along its length and width. It should be understood that the term layer is not necessarily limited to single layers or sheets of materials. In addition, it should be understood that the surfaces of certain layers, including the interface(s) of such layers with other material(s) or layers(s), may be imperfect, wherein said surfaces represent an interpenetrating, entangled or convoluted network with other material(s) or layer(s). Similarly, it should also be understood that a layer may be discontinuous, such that the continuity of said layer along the X-Y dimension may be disturbed or otherwise interrupted by other layer(s) or material(s).
• a material or component is deposited “over” another material or component permits other materials or layers to exist between the material or component being deposited and the material or component "over” which it is deposited.
• a layer may be described as being deposited “over” an electrode, even though there are various materials or layers in between the layer and the electrode.
• absorptivity refers to the percentage of incident light at a given wavelength that is absorbed.
• the organic photosensitive optoelectronic devices of the present disclosure comprise at least one acceptor and/or donor sensitizer to improve the absorption and photoresponse of the acceptor and/or donor layers, respectively.
• the sensitizers are designed such that energy absorbed by a sensitizer may be transferred to a host acceptor or host donor material, the acceptor and donor materials being responsible for exciton transport, charge separation, and charge carrier conduction.
• an organic acceptor material of a photosensitive optoelectronic device may be mixed with an acceptor sensitizer to form a mixed organic acceptor layer.
• the device comprises two electrodes in superposed relation with a mixed organic acceptor layer and an organic donor layer located between the two electrodes.
• the organic donor layer comprises at least one donor material.
• the mixed organic acceptor layer comprises a mixture of an acceptor material and at least one acceptor sensitizer.
• the mixed organic acceptor layer and the donor layer comprise the device's photoactive region, which absorbs electromagnetic radiation to generate excitons that may dissociate into an electron and a hole in order to generate an electrical current.
• the interface between the mixed organic acceptor layer and the donor layer may form a donor-acceptor heterojunction.
• Absorption bands of the acceptor material and the at least one acceptor sensitizer may complement one another to expand the overall absorption of the mixed organic acceptor layer. That is, to optimize absorption, in some embodiments, the acceptor material and the acceptor sensitizer(s) can be chosen such that they do not exhibit substantially similar absorptivity over the same wavelengths. In some embodiments, the at least one acceptor sensitizer has a maximum absorptivity at one or more wavelengths, wherein the maximum
• the at least one acceptor sensitizer has an absorptivity of at least 10 3 cm "1 at one or more wavelengths ranging from 350 to 950 nm. In some embodiments, the at least one acceptor sensitizer has an absorptivity of at least 10 3 cm "1 at one or more wavelengths ranging from 450 to 700 nm.
• An important feature of the present disclosure is efficient transfer of absorbed energy from the at least one acceptor sensitizer to the acceptor material.
• the at least one acceptor sensitizer and the acceptor material should be chosen to satisfy the following conditions:
• the at least one acceptor sensitizer has a lowest triplet excited state
• E T -ASens energy greater than or equal to a lowest triplet excited state energy (E T- A) of the acceptor material
• the at least one acceptor sensitizer has a reduction potential lower than or equal to a reduction potential of the acceptor material
• the at least one acceptor sensitizer and the acceptor material form a charge transfer (CT) state having a CT state energy
• the CT state energy is greater than or equal to the lowest triplet excited state energy (ET-A) of the acceptor material.
• the at least one acceptor sensitizer having a lowest triplet excited state energy (E T -ASens) greater than or equal to the lowest triplet excited state energy (E T -A) of the acceptor material permits Dexter (triplet-triplet) energy transfer between the at least one acceptor sensitizer and the acceptor material.
• This mechanism is shown in Fig. 2B using a Ceo acceptor as an example. If the at least one acceptor sensitizer and the acceptor material form a CT state, a CT state energy greater than or equal to the lowest triplet excited state energy (ET-A) of the acceptor material permits electron transfer to the acceptor material, as shown in Fig. 2C using Ceo as an example.
• the at least one acceptor sensitizer having a reduction potential lower than or equal to the reduction potential of the acceptor material allows for efficient energy transfer by preventing charge separation and/or carrier trapping.
• the acceptor material and the at least one acceptor sensitizer may also be chosen such that the at least one acceptor sensitizer has a lowest singlet excited state energy (E s-A sens) greater than or equal to a lowest singlet excited state energy (ES-A) of the acceptor material. This arrangement permits Forster (singlet- singlet) energy transfer between the at least one acceptor sensitizer and the acceptor material, as shown in Fig. 2A using C&o as an example.
• the acceptor material and the at least one acceptor sensitizer may also be chosen such that the CT state energy, if formed, is greater than or equal to a lowest singlet excited state energy (ES-A) of the acceptor material.
• ES-A lowest singlet excited state energy
• the size and shape of the at least one acceptor sensitizer may substantially match the size and shape of the acceptor material.
• the mixture of the acceptor material and the at least one acceptor sensitizer form a solid solution.
• solid solution means an intimate and random mixture of two or more materials that is a solid at a given temperature, and that has no positional order for any of the components within the solid solution.
• acceptor materials for the present disclosure include but are not limited to polymeric or non-polymeric perylenes, polymeric or non-polymeric naphthalenes, and polymeric or non-polymeric fullerenes and fullerene derivatives (e.g., PCBMs, ICBA, ICMA, etc.).
• PTCBI 10-perylenetetracarboxylicbis- benzimidazole
• PCBM Phenyl-C 6 rButyric-Acid-Methyl Ester
• Phenyl- C 7 Butyric-Acid-Methyl Ester [70]PCBM
• the at least one acceptor sensitizer of the present disclosure may be chosen from, for example, phthalocyanines, subphthalocyanines, dipyrrins and metal complexes thereof, porphyrins, azadipyrrins and metal complexes thereof, boron dipyrromethene (BODIPY) dyes, and derivatives thereof.
• BODIPY boron dipyrromethene
• absorption, singlet and triplet energies, and reduction/oxidation potential of candidate materials for the at least one acceptor sensitizer may be tuned by attaching functional groups.
• functional groups may be attached to extend the ⁇ -conjugation of dipyrrins, azadipyrrins, porphyrins, phthalocyanines, and subphthalocyanines.
• the at least one acceptor sensitizer is a compound having a structure
• M is chosen from B, Al, Ga, In, and Tl;
• X is chosen from halogens, -SCN, alkyl, aryl, -OR, and -SR;
• Ri_i 2 are independently chosen from H and inorganic and organic functional groups such that the conditions for the acceptor material and the at least one acceptor sensitizer are satisfied.
• R- 1 - 12 are independently chosen from -NO 2 , halogens, -CN, -SCN, alkyl, aryl, -OR, -SR, - COOR, -CRO, and H.
• the at least one acceptor sensitizer is a compound chosen from
• X 3 is chosen from
• M is chosen from a metal and boron; n is chosen from 1 , 2, and 3; L is chosen from inorganic and organic ligands with mono- or multiple coordinating sites; Y is a heteroatom; and Ri -n are independently chosen from H and inorganic and organic functional groups such that the conditions for the acceptor material and the at least one acceptor sensitizer are satisfied.
• Ri -n are independently chosen from H and inorganic and organic functional groups such that the conditions for the acceptor material and the at least one acceptor sensitizer are satisfied.
• the at least one acceptor sensitizer is a compound chosen from
• Ri -n are independently chosen from H and inorganic and organic functional groups such that the conditions for the acceptor material and the at least one acceptor sensitizer are satisfied.
• Ri -n are independently chosen from -NO 2 , halogens, -CN, -SCN, alkyl, aryl, -OR, -SR, COOR, -CRO, and H.
• the at least one acceptor sensitizer is a compound chosen from r ,., '' '''' '' % ⁇ - ⁇ >
• X5-8 are independently chosen from
• M is chosen from a metal and boron; Y is a heteroatom; and Ri -n are independently chosen from H and inorganic and organic functional groups such that the conditions for the acceptor material and the at least one acceptor sensitizer are satisfied.
• Ri -n are independently chosen from -N0 2 , halogens, -CN, - SCN, alkyl, aryl, -OR, -SR, -COOR, -CRO, and H.
• the at least one acceptor sensitizer is a compound chosen from
• M is chosen from a metal and boron; n is chosen from 1 , 2, and 3; L is chosen from inorganic and organic ligands with mono- or multiple coordinating sites; Y is a heteroatom; and Ri -n are independently chosen from H and inorganic and organic functional groups such that the conditions for the acceptor material and the at least one acceptor sensitizer are satisfied.
• Ri -n are independently chosen from H and inorganic and organic functional groups such that the conditions for the acceptor material and the at least one acceptor sensitizer are satisfied.
• the at least one acceptor sensitizer of the present disclosure may be a multichromophonc sensitizer.
• the multichromophonc sensitizer has a structure chosen from
• linker is an organic compound
• chromophores 1 to 4 are chosen from dipyrrins, phthalocyanines, subphthalocyanines, porphyrins, and azadipyrrins.
• the multichromophoric sensitizer has a structure chosen from
• each chromophore is directly connected to one or more chromophores, and chromophores 1 to 4 are chosen from dipyrrins, phthalocyanines,
• subphthalocyanines subphthalocyanines, porphyrins, and azadipyrrins.
• the mixed organic acceptor layer may have a thickness in a range of, for example, 5 to 1000 nm, such as 5 to 500 nm, 5 to 150 nm, 10 to 125 nm, 15 to 100 nm, 20 to 90 nm, 20 to 70 nm, or 30 to 60 nm.
• the mixture of the acceptor material and the at least one acceptor sensitizer in the mixed organic acceptor layer has an
• the organic photosensitive optoelectronic devices of the present disclosure may include an intermediate acceptor layer located between the mixed acceptor layer and the donor layer.
• the intermediate acceptor layer may form a donor-acceptor heterojunction with the donor layer.
• the intermediate acceptor layer as recited throughout this disclosure, may consist of the acceptor material.
• the intermediate acceptor layer consists of the acceptor material and other organic material.
• At least 50%, at least 60%, at least 70%, at least 80%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or at least 99.9% of material comprising the intermediate acceptor layer is the acceptor material.
• Inclusion of the intermediate acceptor layer can ensure that excitons charge separate at the interface of the acceptor material and the donor layer.
• the intermediate acceptor layer may have a thickness in a range of, for example, 5 to 1000 nm, such as 5 to 500 nm, 5 to 100 nm, 10 to 50 nm, or 15 to 35 nm.
• the at least one acceptor sensitizer of the present disclosure may comprise two or more acceptor sensitizers.
• the at least one acceptor sensitizer comprises a first acceptor sensitizer and a second acceptor sensitizer.
• the absorption bands of the first acceptor sensitizer, the second acceptor sensitizer, and the acceptor material may complement one another to expand the overall absorption of the mixed organic acceptor layer. That is, in some
• the first acceptor sensitizer, the second acceptor sensitizer, and the acceptor material do not exhibit substantially similar absorptivity over the same wavelengths.
• the first acceptor sensitizer has a maximum absorptivity at one or more wavelengths, wherein the maximum absorptivity of the first acceptor sensitizer is at least twice as large as the absorptivities of the second acceptor sensitizer and the acceptor material, respectively, at the one or more wavelengths.
• the second acceptor sensitizer has a maximum absorptivity at one or more wavelengths, wherein the maximum absorptivity of the second acceptor sensitizer is at least twice as large as the absorptivities of the first acceptor sensitizer and the acceptor material, respectively, at the one or more wavelengths.
• an organic donor material of a photosensitive optoelectronic device can be mixed with a donor sensitizer to form a mixed organic donor layer.
• the device comprises two electrodes in superposed relation with a mixed organic donor layer and an organic acceptor layer located between the two electrodes.
• the organic acceptor layer comprises at least one acceptor material.
• the mixed organic donor layer comprises a mixture of a donor material and at least one donor sensitizer.
• the interface between the mixed organic donor layer and the acceptor layer may form a donor-acceptor heterojunction.
• Absorption bands of the donor material and the at least one donor sensitizer may complement one another to expand the overall absorption of the mixed organic donor layer. That is, in some embodiments, to optimize absorption, the donor material and the donor sensitizer(s) do not exhibit substantially similar absorptivity over the same wavelengths.
• the at least one donor sensitizer has a maximum absorptivity at one or more wavelengths, wherein the maximum absorptivity is at least twice as large as the absorptivity of the donor material at the one or more wavelengths.
• the at least one donor sensitizer has an absorptivity of at least 10 3 cm "1 at one or more wavelengths ranging from 350 to 950 nm.
• the at least one donor sensitizer has an absorptivity of at least 10 3 cm "1 at one or more wavelengths ranging from 450 to 700 nm.
• the at least one donor sensitizer and the donor material should be chosen to satisfy the following conditions:
• the at least one donor sensitizer has a lowest triplet excited state energy ( ⁇ -DSens) greater than or equal to a lowest triplet excited state energy (E T- D) of the donor material;
• the at least one donor sensitizer has an oxidation potential higher than or equal to an oxidation potential of the donor material
• the at least one donor sensitizer and the donor material form a charge transfer (CT) state having a CT state energy
• CT state energy is greater than or equal to the lowest triplet excited state energy (E T- D) of the donor material.
• the at least one donor sensitizer having a lowest triplet excited state energy (E T -DSens) greater than or equal to the lowest triplet excited state energy (E T- D) of the donor material permits Dexter (triplet-triplet) energy transfer between the at least one donor sensitizer and the donor material. If the at least one donor sensitizer and the donor material form a CT state, a CT state energy greater than or equal to the lowest triplet excited state energy (ET-D) of the donor material permits electron transfer to the donor material.
• the at least one donor sensitizer having an oxidation potential higher than or equal to the oxidation potential of the donor material allows for efficient energy transfer by preventing charge separation and/or carrier trapping.
• the donor material and the at least one donor sensitizer may also be chosen such that the at least one donor sensitizer has a lowest singlet excited state energy (E S -DSens) greater than or equal to a lowest singlet excited state energy (E S- D) of the donor material.
• E S -DSens lowest singlet excited state energy
• E S- D lowest singlet excited state energy
• the donor material and the at least one donor sensitizer may also be chosen such that the CT state energy, if formed, is greater than or equal to a lowest singlet excited state energy (ES-D) of the donor material.
• E-D lowest singlet excited state energy
• the size and shape of the at least one donor sensitizer may substantially match the size and shape of the donor material.
• the mixture of the donor material and the at least one donor sensitizer form a solid solution.
• Suitable donor materials for the present disclosure include but are not limited to phthalocyanines, such as copper
• subphthalocyanines such as boron subphthalocyanine (SubPc), naphthalocyanines, merocyanine dyes, boron-dipyrromethene (BODIPY) dyes, thiophenes, such as poly(3-hexylthiophene) (P3HT), polyacenes, such as pentacene and tetracene, diindenoperylene (DIP), and squaraine (SQ) dyes.
• SubPc boron subphthalocyanine
• naphthalocyanines merocyanine dyes
• BODIPY boron-dipyrromethene
• thiophenes such as poly(3-hexylthiophene) (P3HT)
• P3HT poly(3-hexylthiophene)
• polyacenes such as pentacene and tetracene
• DIP diindenoperylene
• SQL squa
• squaraine donor materials include but are not limited to 2,4-bis [4-(N,N-dipropylamino)-2,6-dihydroxyphenyl] squaraine, 2,4-bis[4-(N,N- diisobutylamino)-2,6-dihydroxyphenyl] squaraine, 2,4-bis[4-(N,N-diphenylamino)-2,6- dihydroxyphenyl] squaraine (DPSQ) and salts thereof. Additional examples of suitable squaraine materials are disclosed in U.S. Patent Publication No.
• the at least one donor sensitizer may be chosen, for example, from subphthalocyanines, porphyrins, phthalocyanines, dipyrrins and metal complexes thereof, boron dipyrromethene (BODIPY) dyes, squaraines, oligothiophenes, acenes and derivatives thereof.
• the at least one donor sensitizer may be chosen from any of compounds 1 to 31 as described herein. It should be appreciated that absorption, singlet and triplet energies, and reduction/oxidation potential of candidate materials for the at least one donor sensitizer may be tuned by attaching functional groups.
• the mixed organic donor layer may have a thickness in a range of, for example, 5 to 1000 nm, such as 5 to 500 nm, 5 to 150 nm, 10 to 125 nm, 15 to 100 nm, 20 to 90 nm, 20 to 70 nm, or 30 to 60 nm.
• the mixture of the donor material and the at least one donor sensitizer in the mixed organic donor layer has a dononsensitizer ratio in a range of 10: 1 to 1 :2.
• the organic photosensitive optoelectronic devices of the present disclosure may include an intermediate donor layer located between the mixed donor layer and the acceptor layer.
• the intermediate donor layer may form a donor-acceptor heterojunction with the acceptor layer.
• the intermediate donor layer may consist of the donor material. In some embodiments, the intermediate donor layer consists of the donor material and other organic material. In some
• the intermediate donor layer is the donor material. Inclusion of the intermediate donor layer can ensure that excitons charge separate at the interface of the donor material and the acceptor layer.
• the intermediate donor layer may have a thickness in a range of, for example, 5 to 1000 nm, such as 5 to 500 nm, 5 to 100 nm, 10 to 50 nm, or 15 to 35 nm.
• organic photosensitive optoelectronic devices of the present disclosure may comprise both a mixed acceptor layer and a mixed donor layer.
• the mixed acceptor layer comprises a mixture of an acceptor material and at least one acceptor sensitizer as described herein.
• the mixed donor layer comprises a mixture of a donor material and at least one donor sensitizer as described herein.
• absorption bands of the acceptor material and the at least one acceptor sensitizer may complement one another to expand the overall absorption of the mixed organic acceptor layer.
• the absorption bands of the donor material and the at least one donor sensitizer may complement one another to expand the overall absorption of the mixed organic donor layer.
• the sensitizers may be chosen to maximize the absorption overlap of the mixed acceptor and donor layers within the solar spectrum. This may involve choosing sensitizers that absorb in different wavelength ranges. Alternatively, sensitizers with partial or full overlap of their absorption spectra may be chosen to maximize the thin film absorptivity of the mixed donor and acceptor layers in a given wavelength range.
• the devices with a mixed organic acceptor layer and a mixed organic donor layer may include an intermediate acceptor layer as described herein and an intermediate donor layer as described herein.
• the intermediate acceptor layer is adjacent to the mixed organic acceptor layer, and the intermediate donor layer is adjacent to the mixed organic donor layer, both intermediate layers being positioned between the mixed organic acceptor layer and the mixed organic donor layer.
• the intermediate acceptor layer and the intermediate donor layer may form a donor-acceptor heterojunction.
• the intermediate layers may have thicknesses as described herein.
• One of the electrodes of the present disclosure may be an anode, and the other electrode a cathode. It should be understood that the electrodes should be optimized to receive and transport the desired carrier (holes or electrons).
• the term "cathode” is used herein such that in a non-stacked PV device or a single unit of a stacked PV device under ambient irradiation and connected with a resistive load and with no externally applied voltage, e.g., a PV device, electrons move to the cathode from the photo-conducting material.
• the term “anode” is used herein such that in a PV device under illumination, holes move to the anode from the
• photoconducting material which is equivalent to electrons moving in the opposite manner.
• the optoelectronic devices such as organic PVs, may have a conventional or inverted structure.
• inverted device structures are disclosed in U.S. Patent Publication No. 2010/0102304, which is incorporated herein by reference for its disclosure of inverted device structures.
• the organic photosensitive optoelectronic devices of the present disclosure may further comprise additional layers as known in the art for such devices.
• devices may further comprise charge carrier transport layers and/or buffers layers such as one or more blocking layers, such as an exciton blocking layer (EBL).
• EBL exciton blocking layer
• One or more blocking layers may be located between the photoactive region and either or both of the electrodes.
• materials that may be used as an exciton blocking layer include bathocuproine (BCP), bathophenanthroline (BPhen), 1 ,4,5,8- Naphthalene-tetracarboxylic-dianhydride (NTCDA), 3,4,9,10- perylenetetracarboxylicbis-benzimidazole (PTCBI), 1 ,3,5-tris(N-phenylbenzimidazol- 2-yl)benzene (TPBi), tris(acetylacetonato) ruthenium(lll) (Ru(acac) 3 ), and
• the organic photosensitive optoelectronic devices of the present disclosure may comprise additional buffer layers as known in the art for such devices.
• the devices may further comprise at least one smoothing layer.
• a smoothing layer may be located, for example, between the photoactive region and either or both of the electrodes.
• a film comprising 3,4- polyethylenedioxythiophene:polystyrenesulfonate (PEDOT:PSS) is an example of a smoothing layer.
• the organic optoelectronic devices of the present disclosure may exist as a tandem device comprising two or more subcells.
• a subcell as used herein, means a component of the device which comprises at least one donor-acceptor heterojunction. When a subcell is used individually as a photosensitive
• a tandem device typically includes a complete set of electrodes.
• a tandem device may comprise charge transfer material, electrodes, or charge recombination material or a tunnel junction between the tandem donor-acceptor heterojunctions.
• adjacent subcells it is possible for adjacent subcells to utilize common, i.e., shared, electrode, charge transfer region or charge recombination zone. In other cases, adjacent subcells do not share common electrodes or charge transfer regions.
• the subcells may be electrically connected in parallel or in series.
• the recombination layer may be chosen from Al, Ag, Au, M0O 3 , Li, LiF, Sn, Ti, WO 3 , indium tin oxide (ITO), tin oxide (TO), gallium indium tin oxide (GITO), zinc oxide (ZO), or zinc indium tin oxide (ZITO).
• the charge transfer layer or charge recombination layer may be comprised of metal nanoclusters, nanoparticles, or nanorods.
• the donor-acceptor heterojunctions recited herein are chosen from a mixed heterojunction, a bulk heterojunction, a planar heterojunction, a nanocrystalline-bulk heterojunction, and a hybrid planar-mixed heterojunction.
• the devices of the present disclosure may be, for example, photodetectors, photoconductors, or PV devices, such as solar cells.
• a method of fabricating an organic photosensitive optoelectronic device comprises depositing a photoactive region over a first electrode, and depositing a second electrode over the photoactive region (Fig. 8).
• the photoactive region may comprise a mixed organic acceptor layer and an organic donor layer (e.g., Fig. 1 ), wherein the mixed organic acceptor layer comprises a mixture of an acceptor material and at least one acceptor sensitizer, as described herein.
• the acceptor material and the at least one acceptor sensitizer are chosen to satisfy the conditions described herein for the mixed organic acceptor layer.
• depositing a photoactive region over a first electrode comprises depositing the organic donor layer over the first electrode, and co-depositing the acceptor material and the at least one acceptor sensitizer over the first electrode.
• the co-deposition of the acceptor material and the at least one acceptor sensitizer over the first electrode may occur before or after the deposition of the organic donor layer over the first electrode.
• the organic donor layer should be deposited over the first electrode before the co- deposition of the mixed organic acceptor layer. If the first electrode is optimized to receive and transport electrons, the mixed acceptor layer should be deposited over the first electrode before deposition of the organic donor layer.
• the photoactive region further comprises an intermediate acceptor layer, as described herein (e.g., Fig. 3).
• an intermediate acceptor layer as described herein (e.g., Fig. 3).
• depositing a photoactive region over a first electrode may comprise depositing the organic donor layer over the first electrode, depositing the
• the co- deposition of the acceptor material and the at least one acceptor sensitizer over the first electrode may occur before or after the deposition of the organic donor layer, wherein the deposition of the intermediate acceptor layer results in the intermediate acceptor layer being positioned between the mixed acceptor layer and the organic donor layer.
• the organic donor layer of the photoactive region is a mixed organic donor layer comprising a mixture of a donor material and at least one donor sensitizer, as described herein (e.g., Fig. 4).
• the donor material and the at least one donor sensitizer are chosen to satisfy the conditions described herein for the mixed organic donor layer.
• depositing a photoactive region over a first electrode may comprise co-depositing the donor material and the at least one donor sensitizer over the first electrode, and depositing the organic acceptor layer over the first electrode.
• the co-deposition of the donor material and the at least one donor sensitizer may occur before or after the deposition of the organic acceptor layer.
• the deposition of the organic acceptor layer may comprise co-deposition of the acceptor material and the at least one acceptor sensitizer.
• the deposition of the photoactive region also comprises depositing the intermediate acceptor layer such that the intermediate acceptor layer is positioned between the mixed organic acceptor layer and the mixed organic donor layer.
• the photoactive region further comprises an intermediate donor layer, as described herein (e.g., Fig. 5).
• depositing a photoactive region over a first electrode may comprise co-depositing the donor material and the at least one donor sensitizer over the first electrode, depositing the intermediate donor layer over the first electrode, and depositing the organic acceptor layer over the first electrode.
• the co-deposition of the donor material and the at least one donor sensitizer may occur before or after the deposition of the acceptor layer, wherein the deposition of the intermediate donor layer results in the intermediate donor layer being positioned between the mixed organic donor layer and the organic acceptor layer.
• the deposition of the organic acceptor layer may comprise co-deposition of the acceptor material and the at least one acceptor sensitizer.
• the deposition of the photoactive region also comprises depositing the intermediate acceptor layer such that the intermediate acceptor layer is adjacent to the mixed organic acceptor layer, and the intermediate donor layer is adjacent to the mixed organic donor layer, both intermediate layers being positioned between the mixed organic acceptor layer and the mixed organic donor layer.
• the ratio of the acceptor material to the at least one acceptor sensitizer during co-deposition in any of the embodiments described herein, may be in a range of 10:1 to 1 :2
• the ratio of the donor material to the at least one donor sensitizer during co-deposition in any of the embodiments described herein, may be in a range of 10:1 to 1 :2.
• additional layers such as blocking layers, smoothing layers, and other buffer layers known in the art for organic photosensitive optoelectronic devices may be deposited during fabrication of the devices.
• Layers and materials may be deposited using techniques known in the art.
• the layers and materials described herein can be deposited from a solution, vapor, or a combination of both.
• the organic materials or organic layers can be deposited via solution processing, such as by one or more techniques chosen from spin-coating, spin-casting, spray coating, dip coating, doctor-blading, inkjet printing, or transfer printing.
• the organic materials may be deposited using vacuum evaporation, such as vacuum thermal evaporation, organic vapor phase deposition, or organic vapor-jet printing.
• ZCI zinc dipyrrin derivative
• 5-Mesityldipyrromethane was synthesized as follows: a mixture of mesitaldehyde (7 g, 47.2 mmol) and pyrrole (500 mL, 7.2 mol) in a 1000-mL single-neck round-bottomed flask was degassed with a stream of nitrogen for 10 min. MgBr 2 (4.60 g, 25.0 mmol) was added, and the mixture was stirred for 1 .5 h at room temperature. The tan mixture was treated with powdered NaOH (15.0 g, 380 mmol). The mixture was stirred for 1 h and then filtered. The filtrate was concentrated, and the pyrrole was recovered.
• ZCI was then synthesized as follows: 0.62 g (2.34 mmol) of 5- Mesityldipyrromethane was dissolved in 60 mL freshly distilled THF. The solution was cooled using a dry ice/acetone bath. N 2 was bubbled through the reaction mixture for 5 min. 2.2 g (16.4 mmol) of N-chlorosuccinimide (NCS) in 70 mL of THF was slowly added to DPM solution. The reaction mixture was stirred for 2 hours in dry ice/acetone bath under N 2 in the dark. The reaction was allowed to slowly warm to room temperature for 10 hours. THF was evaporated and the crude products were dissolved in 300 ml. dichloromethane (DCM).
• DCM dichloromethane
• the crude products were washed with NaHC0 3 solution and dried over Na 2 S0 4 .
• the dark red products in DCM were used without further purification.
• 2.5 g Zn(OAc) 2 -2H 2 0 in 30 mL CH 3 OH was added to the products in DCM.
• the reaction mixture was stirred overnight at which point the solvent was evaporated.
• the products were dissolved in DCM and the inorganic solid was filtered off.
• the solution was washed with Na 2 C03.
• DCM was evaporated.
• the crude product was passed through a short neutral Al 2 03 column using DCM/hexanes (1/4). 0.4 g of the dark red product was collected.
• the product was dissolved in DCM and recrystallized by layering MeOH on top.
• the product was further purified by gradient sublimation under vacuum (10 "5 torr) at 270°C-200°C-140°C gradient temperature zones.
• the product ZCI was a mixture of two compounds: C 3 6H 22 CI-i 2 N 4 Zn and C 36 H 23 C iN 4 Zn with molar ratio 3:1 (general formula: Ci 44 H 8 9CI 47 Ni 6 Zn 4 ).
• a single crystal of ZCI was grown by slow thermal sublimation under vacuum, and the mixture of C 3 6H 22 Cli 2 N 4 Zn and C 36 H 23 Cli-
• the structure was determined by X-ray diffraction measurement and is shown in Fig. 10.
• Fig. 1 1 A Absorption (solid square) and emission (open circle) spectra of ZCI in methyl cyclohexane at room temperature are shown in Fig. 1 1 A.
• the inset is the emission from the triplet state of ZCI.
• Absorption (solid symbols) and emission (open symbol) spectra of a C6o film (square) and a ZCI film (triangle) are shown in Fig. 1 1 C.
• Fig. 1 1 D shows cyclic voltammetry (CV) and differential pulse voltammetry (DPV) diagrams of ZCI in dichloromethane (scan rate 100 mV/s).
• CV cyclic voltammetry
• D differential pulse voltammetry
• IrDP iridium dipyrrin derivative
• IrDP was then synthesized as follows: 2,3-dichloro-5,6 dicyano-1 ,4- benzoquinone (DDQ) (1 mmol) was added to a solution of dipyrromethane (1 mmol) in 20 mL of dry tetrahydrofuran (THF) and was stirred at room temperature for 1 hr. A large excess of potassium carbonate (2 g) was then added, and the mixture was stirred for 15 min followed by the addition of [lrCI(f 2 ppy)] 2 (0.5 mmol). The solution was then refluxed under N2 overnight. After cooling to room temperature, solids were removed by vacuum filtration and washed with dichloromethane (3 x 100mL). The collected filtrate was then evaporated to dryness under reduced pressure. The crude product was then passed through a silica gel column using
• Fig. 13B shows a cyclic voltammetry diagram for IrDP (scan rate 100 mV/s).
• Fig. 13C shows absorption (solid symbols) of a ⁇ film (square) and an IrDP film (triangle) and emission (open symbol) of IrDP under excitation at 500 nm.
• the mixed C6o:ZCI films were compared to films of Ceo mixed with two other zinc dipyrrin derivatives, ZH and ZMe, respectively, having the following
• ZH and ZMe have similar singlet and triplet energies as ZCI, but have lower oxidation potentials.
• C 60 is mixed with ZH and ZMe, respectively, electron transfer from ZH and ZMe to Ceo occurs upon light excitation forming charge transfer (CT) states
• CT charge transfer
• C 6 o:ZCI acceptor layer devices were fabricated using squaraine as the donor layer.
• the squaraine structure, device structures, and results are shown in Figs. 23A, 23B, and 23C, respectively.
• a dip in EQE was observed at 550 nm.
• ZCI as an acceptor sensitizer (device D2) fills the dip, resulting in 1 mA/cm 2 increase in photocurrent.
• the AM1 .5G solar spectrum is compared to the thin film extinction spectra of the active materials in Fig. 24A.
• Extinction coefficients for the thin films were calculated from optical constants measured by variable angle spectroscopic ellipsometry.
• Steady-state emission measurements in the thin film and solutions were performed using a Photon Technology International QuantaMaster Model C- 60SE spectrofluorimeter.
• Fig. 25 The reduction potential and singlet and triplet energies of ZCI, CleSubPc, and Ceo are given in Fig. 25.
• the arrows in Fig. 25 outline a schematic for energy transfer pathways from ZCI and CleSubPc to Ceo- Both ZCI and CleSubPc should function as sensitizers, as their singlet and triplet energies are greater than or equal to that of Ceo ensuring that any excitons generated on the sensitizers will be transferred to Ceo and not trapped on the sensitizer. Additionally, the reduction potentials of the sensitizers are less than that of Ceo ensuring that electrons are conducted out via C 6 o-
• Lamellar OPV devices were fabricated to illustrate the impact of sensitization on device performance. Devices were grown on glass substrates with 150 nm indium tin oxide patterned in 2 mm stripes. Prior to deposition, the substrates were cleaned in a surfactant and a series of solvents as described previously and then exposed to ozone atmosphere for 10 min immediately before loading into the high vacuum chamber (base pressure ⁇ 10 "6 torr). M0O3 was thermally evaporated at 0.02 nm/s.
• the sensitized devices contained a blended later of
• EQE measurements were carried out with an illumination area larger than that defined by the cathode.
• Routine spectral mismatch corrections were performed using a silicon photodiode calibrated at National Renewable Energy Laboratory. Chopped and filtered monochromatic light (250 Hz, 10 nm fwhm) from a Cornerstone 260 1/4 M double grating monochromator (Newport 74125) was used in conjunction with an EG&G 7220 lock-in amplifier to perform all EQE and spectral mismatch correction measurements. EQE measurements were carried out with an illumination area smaller than that defined by the cathode.
• FIG. 26A Device structures are shown in Fig. 26A.
• D/A donor/acceptor
• EQE external quantum efficiency
• the open circuit voltage (V oc ) of the NPD sensitized and unsensitized devices remained unchanged at 0.87 V, indicating that the preservation of the D/A interface achieved its desired effect.
• the fill factor (FF) of the devices were 0.47 and 0.49 for both the
• the photoresponse increase from a short circuit current (J sc ) of 3.0 mA/cm 2 (NPD) to 4.3 mA/cm 2 (NPD(s)).
• J sc short circuit current
• NPD 3.0 mA/cm 2
• NPD(s) 4.3 mA/cm 2
• the EQE revealed that in the sensitized device, the increase in response was due to both ZCI and C ⁇ SubPc absorption.
• Sensitization led to a marked increase in photocurrent from Jsc 6.5 mA/cm 2 to 8.6 mA/cm 2 for DPSQ and DPSQ(s), respectively.
• the final device had broadband spectral coverage with EQE in excess of 20% from ⁇ 350 nm to 800 nm.
• Lamellar OPV devices were fabricated to illustrate the impact of donor sensitization on device performance.
• a squaraine donor was sensitized with SubPc.
• Fabricated device structures are shown in Fig. 27A.
• Current- voltage (J-V) and external quantum efficiency (EQE) characteristics for the devices are shown in Fig. 27B, and performance parameters are summarized in the table below.
• the open circuit voltage (V oc ) of the devices increased on the inclusion of the SubPc sensitizer from 0.68 V to 0.93 V.
• the fill factor (FF) remained unaltered at 0.49 for both devices, respectively.
• the photoresponse also remained unchanged at a Jsc of 6.2 mA/cm 2 .
• the EQE revealed that in the sensitized device, response was due to both SubPc and Sq absorption.
• the SubPc contribution was evident between ⁇ 500 nm and 650 nm.
• the unaltered Jsc and FF combined with the increase in Voc resulted in a power conversion efficiency ( ⁇ ⁇ ) increase from 2.1 % (Sq) to 2.8 % (Sq:SubPc) on sensitization.

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